1. Field of the Invention
The present invention relates to an image pickup unit including an image pickup optical system and a backside illuminated image pickup device, and a method of manufacturing the image pickup unit.
2. Description of the Related Art
Conventionally, solid-state image pickup devices (hereinafter simply referred to as image pickup devices) such as CCDs and CMOSs, which pick up images of a subject by converting light entering a light-receiving section provided on a semiconductor substrate into an electrical signal, are well known.
In addition, while such an image pickup device is used in electronic endoscopes, camera-equipped cell-phones, digital cameras, and the like as an image pickup unit in combination with an image pickup optical system, when manufacturing such an image pickup unit, an image pickup optical system must be arranged with high positional accuracy in the direction of an optical axis of the image pickup optical system (hereinafter simply referred to as an optical axis direction) with respect to a light-receiving surface of a light-receiving section of the image pickup device. This is because if the image pickup optical system is arranged displaced in the optical axis direction with respect to the light-receiving surface, a focal position of the subject whose image is formed on the light-receiving section via the image pickup optical system becomes displaced.
In consideration thereof, Japanese Patent Application Laid-Open Publication No. 2009-005328 discloses a configuration of an image pickup unit structural body in which a light-receiving surface of a light-receiving section of an image pickup device is provided with a first optical system that functions as a cover glass for protecting the light-receiving surface and a lens frame for holding a second optical system is mounted on the first optical system, wherein a position of the second optical system in a direction of an optical axis with respect to the light-receiving surface of the image pickup device is defined using a surface of the first optical system on the side of the second optical system as a reference.